Based on almost 20 years of experience in human intervention research with high methodological standards, the Institute for Medical Physics of the University Erlangen-Nuremberg has now intensified its efforts in the field of ‘innovative training and rehabilitation technologies’. Following various new possibilities of application, we quickly began to focus our research on whole- body electromyostimulation (WB-EMS). This interest is reflected in a multitude of training studies which not only address different acute questions and problems concerning WB-EMS but are also of interest for different population groups.
The following overview shows some of the issues which we regard as of particular interest, such as (1) WB-EMS in older people, (2) the discussion of low vs. medium frequency, (3) WB-EMS combined with endurance training, (4) possible acute health consequences after reckless application and (5) WB-EMS effects on body composition and strength parameters compared with HIT-training protocols closely synchronized in duration. We hope this will motivate the reader to reflect on and share our thoughts and motivations.
WB-EMS – studies in older people
As a department of research into musculoskeletal diseases we study the consequences of physical training on muscle and bone parameters in elderly people. Even during recruitment one frequently gets the impression of mainly reaching those who are doing sport anyway. A feeling often confirmed during the baseline measurements of interventions. In fact, statistics show that just a minority of 30 % of elderly people are sufficiently active enough to generate a positive impact on muscle and bone. Lifetime sports abstainers in particular show justifiably less enthusiasm for starting (or being able to start) a conventional training program with appropriate intensity and frequency.
Alternative training technologies such as WB-EMS might be a way of providing independent prevention and therapy that offers joint-friendliness, time-efficiency and a certain exclusivity.
To investigate the effectivity, applicability and attractiveness of WB-EMS in elderly, underperforming and less sport affine people, we conducted the “Training and ElectromyoStimulation Trials” (TEST) series. Here we mainly addressed sedentary older people (60 - 90 years) in randomized controlled studies (RCTs) with adequate statistical power using “gold standard” measurements.
For our first trail (TEST I) (Kemmler, Teschler, & Von Stengel, 2015) we selected women (60+) with experience in strength training. Initially we put the emphasis on evaluating the feasibility, acceptance and effectiveness of this type of intervention (WB-EMS, 1.5 x 20 min/week, 14 weeks) in women with experience in (strength) training together with good resilience and positive physical feeling.
Besides high acceptance and compliance, we found (significant) improvements in muscle mass, body fat, strength and power compared with a group which just continuing its conventional exercise training.
Motivated by the positive results of TEST I we ventured on a more “crucial” intervention group in TEST II (Kemmler, Teschler, & Von Stengel, 2015), made up of untrained and physically inactive men (65+) with cardio-metabolic diseases and abdominal obesity. The central aim was the enhancement of lean body mass (LBM) and reduction of abdominal body fat level both total and also with a negative cardio-metabolic effect. After 14 weeks of WB-EMS (1.5 x 20 min/week) we verified (significant) differences for LBM and total body fat, as well as a tendency for reduction in abdominal fat compared with a control group (vibration training, 2 x 15 min/week). There were no effects in laboratory findings (e.g. cholesterol) or blood pressure. Beside highly significant improvements in strength and power, the interventions once again showed high attractiveness and compliance.
For the very elaborate TEST III study (Kemmler, Teschler, & Von Stengel, 2015), we focused on an even more vulnerable population of physical inactive women (70+) with low muscle mass and bone density. The central aim was the increment of muscle mass and bone density compared with a control group doing a low-impact functional training. After one year of intervention (WB-EMS, 1.5 x 20 min/week) TEST III showed highly relevant improvements in muscle mass/function and body fat. Effects on bone density were clearly significant, but compared with muscle mass in an unspectacular range, better comparable to mean values known from whole-body vibration. Here, we expected more obvious results, expecting a closer “muscle-to-bone interaction”. Overall, the TEST III conclusion is none the less positive, not least because we (again) had a high compliance with low dropout and high attendance.
WB-EMS induced energy expenditure and cardio metabolic effects were evaluated in TEST IV (Kemmler et al., 2016). These results will be presented at a later point in time (see below) so that we will continue by concentrating on TEST V (FORMOsA study). TEST V addressed the particularly crucial group of independently living elderly women (70+) with sarcopenic obesity, in other words people with very poor muscle mass/-function and concurrent high body fat. In view of the assumed functional limitations in this group, we gave up the usual (easy) EMS-accompanying movements in a standing position, and opted to conduct WB-EMS applications in a supine position instead. A previous pilot study showed significantly higher effects for power, muscle strength and mass when comparing an active WB-EMS application performing movement patterns during the impulse phase with a solely passive application. However, this very weak group showed highly significant effects on strength and power even after passive WB-EMS in a supine position. After the 6-month TEST V period, we found highly significant gains in a sarcopenia index based primarily on increased muscle mass and less on improvements in functional capacities (gait speed, grip strength). Because of an initially high protein intake (1 g/kg/body weight) these effects are independent of our accompanying protein supplementation of 0.4 g/kg/body weight. Despite a potential and certain existing need through initially more than 35 % of body fat, we could not show significant effects on total and abdominal fat. Surprisingly and contrary to TEST III, we found highly relevant and significant changes in cardio metabolic risk factors arising from the “metabolic syndrome”. TEST V showed that training in a supine position with additional movement patterns is suboptimal for developing important functional parameters like “strength”, “power”, “balance” and “gait speed” in elderly and so it should only be applied to corresponding limited populations.
Following the Formosa study, we organized a somewhat similar study to examine sarcopenic obesity in men 70+ (FranSO). During the training sessions, we dropped the supine position in favour of training in the more usual standing position. Compared with the FORMOsA study, we increased the individual protein intake to a total of 1.8 g/kg body weight.
After 14 weeks of WB-EMS Training (1.5 weeks / week, 12 - 20 min progressive, see above), we found significant improvements in almost all parameters. In addition to the total body fat, abdominal body fat was significantly reduced with simultaneous improvement of the skeletal muscle mass index, functional abilities (strength) and more favorable developments in the blood values (e.g. cholesterol/blood fats). As in the previous study, all conditions (nutrition, physical and sporting activity) were kept stable over the intervention period.
Despite the reasons mentioned above it is quite informative to compare the effects of WB-EMS to (strength) training protocols in elderly people. From the available literature, at least half of the average intense (strength) training protocols show less positive results than WB-EMS. Focusing on strength, conventional muscle training seems to show higher outcomes in maximal strength and substantial increments in power (e.g. performance or speed strength). Quite similar are the effects for reduction in body fat mass, always bearing in mind the higher training volume in conventional programs. There is no doubt, however, about the dominance of conventional sport training programs on the endpoint “bone density”, while values from WB-EMS are in the range of whole-body vibration training.
From our TEST studies we concluded that in elderly people not willing or able to perform conventional body training for a wide range of reasons, WB-EMS represents an independent option for prevention and therapy. Though the effects are not that extensive (e.g. effects on endurance), the barriers that usually limit prolonged implementation are none the less lower. In additional, WB-EMS is widely regarded as an attractive, appropriate and efficient training method with no fundamental risk factors assuming that the exclusion criteria are heeded, there is proper preparation and sensible application. Then, and from the actual state of research, WB-EMS can be regarded as a time-efficient option for an independent, musculoskeletal prophylaxis and improvement of functional capacities.
Different impulse frequencies during WB-EMS – an evidence-based review
Articles found on the WWW about WB-EMS frequently suggest the dominance of modulated middle frequency (≈2 Hz) (MET) over low frequency EMS (≈<100 Hz). At a first glance, the effects quoted sound quite reasonable and supported by experience from neuromuscular electrical stimulation (NMES). Thus, MET currents are mostly used in therapy with advantages for certain muscle activation diseases and also linked to a reduced sensation load (pain!) (See below). However, there is heated discussion about this kind of current for the effectiveness on muscle training in healthy subjects.
We want to address this topic free of ideology and with clear reference to the existing scientific literature. Summarized, a sophisticated search in the appropriate scientific literature databases (e.g. Medline, PEDro) found only 5 investigations directly comparing low and medium frequency of (local) EMS. Just one of these studies examined the question on a longitudinal basis over 3 weeks (Stefanovska & Vodovnik, 1985) and shows almost a twofold improvement in the strength for leg extension in low frequency EMS application (25 Hz) compared with MET (2,500 Hz/25 Hz). With one exception, all the other (cross-sectional) studies looking for similar effects show more favorable developments for low frequency EMS application in acute strength development and fatigue. No consistent results can be found for discomfort or experience of pain during EMS application.
Summarizing the available literature, there is nothing to suggest the dominance of MET. Furthermore, there are hardly any reliable data from investigations of high quality, and what there are but if, depending on endpoints, differ strongly from low frequency EMS application. Of course frequently reported positive effects of MET are not ruled out, but try to postulate a dominance of MET from professional and evidence-based research could be clutching at straws.
Combining WB-EMS and endurance training
A combination of both training methods, WB-EMS and endurance, is used by many coaches for enhanced effects for the cardiovascular system and especially for body fat reduction.
Concerning the first effect, one study (Fritzsche et al., 2010) evaluated the influence of conventional low frequency training (see above; in standing position) on cardiac and functional parameters in patients with heart insufficiency. After 6 months, the authors found an improvement in muscle physiological and metabolic parameters “by far exceeding the results of common traditional aerobic training forms”. Consequently, the combination of both methods (WB-EMS with additional endurance training) should generate optimum results, also with a certain relevance for mobile WB-EMS application. In contrast to Fritzsche et al., we primarily focused on the effect of a combined WB-EMS/endurance intervention on metabolic syndrome and energetic metabolism in overweight and obese men (Kemmler, Von Stengel, Schwarz, & Mayhew, 2012). It was also one of our aims to closely examine the “impressive” effect on body fat reduction given that WB-EMS is a training method requiring relatively litte time (1.5 x 20 min/week). To capture the energy expenditure with and without WB-EMS we used the “gold standard” method of indirect calorimetry (resp. analysis of breathing gas). We found significantly higher energy expenditure after a classic 16-min WB-EMS application with additional light movement patterns in a standing position (intermitted, 85 Hz; see above) and a similar trend for the 30-min endurance program (cross-trainer) with 60 % of maximum oxygen intake under “continuous current” (7 Hz vs. 85 Hz; 350 µs). However, this energy expenditure for the classic EMS application (107 ± 16 vs. 92 ± 17 kcal/16 min) is borderline negligable. Concerning the cross-trainer endurance program, the very low frequency (7 Hz) showed clear effects (500 ± 67 vs. 85 Hz: 476 ± 68 vs. No EMS: 450 ± 60 kcal/30 min). Especially the marginal effects from classic EMS application are somehow at odds with the obvious fat reduction with WB-EMS. Reconsidering EMS-induced higher energy expenditure, there are three possible mechanisms: (1) the energy need during acute load (see above), (2) excess post-exercise oxygen consumption (meaning intermediate effects over several hours post-training) and (3) an increased resting metabolic rate conditioned by EMS-induced increase in muscle mass. While (3), more for medium to long-term effects, plays a not inconsiderable role for weight or “fat management”, point (2) is frequently overrated because the total energy used amounts to 10 - 15 % of the immediate load.
Methodically debatable is the question, whether our spirometric measurement really captured the actual energy consumption during WB-EMS with the simultaneous stimulation of 2,800 cm2 of body surface (point (1)). Actually, indirect calorimetry is less suitable for measuring energy consumption during mainly local and anaerobic energy supply such as strength training or WB-EMS. More sophisticated methods should therefore be used to address this topic.
Careful use with initally too high intensity during EMS
In 2015, SpiegelOnline magazine ran an article with headline “dangerous current impulses“ that aptly described the problem of (too) high initial current intensity in WB-EMS in beginners: dizziness, nausea and high creatine kinase (CK) values with corresponding possible stress for the kidneys – certainly not the best motivation for a potential user. What is the real “truth” behind these reported, almost unbelievably high, CK values after (too) intense initial application – which is certainly also a problem that could have a clinical relevance in our research area with older people. In order to clarify this problem we conducted a study with three questions (Kemmler, Teschler, Bebenek, & von Stengel, 2015; Teschler, 2016): (1) Are the CK values as high as sometimes reported in the literature after WB-EMS application to exertion (85 Hz, 20 min, intermittent, see above)? (2) Does rhabdomyolysis (muscle decay) have clinical relevance in healthy users? (3) Does regular WB-EMS lead to a reduction in CK values after exertion?
Question 1 can definitely be answered with a clear “yes”! In fact, we found a 117-fold increase in CK in comparison to resting value (170 IE/l). Twenty-six sporting subjects (25 - 50 y) without WB-EMS experience did one single bout of WB-EMS to exertion, with CK peaking after 3 - 4 days. The maximum value was about 144,000 IE, a result confirmed by recently reported even higher values (240,000 IE) in young professional soccer players after WB-EMS to exhaustion (Kastner, Braun, & Meyer, 2014). In fact, WB-EMS application meets all the above-mentioned criteria for training-induced CK levels such as (a) high proportion of upper body musculature, (b) high volume of exercised muscles, (c) short breaks, (d) high innervation rate, and (e) mechanical stress.
On the other hand, question 2 can not be answered that easily. A pronounced stress-induced (“exertional”) rhabdomyolysis is defined as values of more than 10,000 IE/l or a 50-fold increase in resting value, and can be associated with considerable health complications. Beside (heart-) muscle-related problems caused by hyperkalemia and hypocalcemia, as well as liver damage, acute renal failure is frequently reported after (trauma-induced) rhabdomyolysis. In this context, we evaluated not only parameters for rhabdomyolysis (e.g. CK, myoglobin), but also electrolytes (e.g. potassium, calcium) and kidney parameters such as creatinine concentration, glomular filtration rate, as well as traces of protein and blood in the urine. We found no abnormalities in electrolytes or for the kidneys and the urine parameters, despite a 40-fold increase in myoglobin, which is considered as “nephrotoxic“. Thus, no cause for concern? Certainly not, all our study participants were healthy, fit and well hydrated and were also guided and supervised very closely by medical staff. The extent to which an initial application to exertion can lead to renal impairment in people with poor preparation remains undecided.
Turning to question 3: Due to a “repeated bout effect”, CK concentration (as guiding criteria for rhabdomyolysis) increases only about 4 - 5 fold after a 10-week conditioning training (1 x 20 min/week) and thus lies in the range of intense conventional strength training. Approaching the present topic with a certain degree of common sense, exertional CK values should not occur during the first sessions/trial session. In training, however, especially competitive/performance-oriented novices with a certain tolerance for high loads demand exactly this kind of exertional stress, a request which is often heeded by EMS trainers. Again, due to the supramaximal intensity and the large amount of simultaneously trained muscles in WB-EMS, a reckless application is particularly “prone” to provoking “exertional rhabdomyolysis” with all its associated health consequences. Therefore, a slow approach to higher current intensities should be paramount during a 4 - 6-week conditioning phase.
Effectiveness of WB-EMS compared with conventional strength training methods
Twelve times greater effects of WB-EMS Training versus conventional strength training – to be honest, not even the keenest WB-EMS supporter would believe this. In fact, the myth comes from a scientific study which showed a 12-fold higher CK concentration after WB-EMS compared with classic strength training. We now know about the significant effects of WB-EMS on body composition and functional capacities (see above). However, the question is to what extent WB-EMS can compete with a similar time-effective training protocol such as high-intensity (strength) training (HIT). To answer this question, we conducted a study with men aged 30 - 50 years – certainly one of the few groups for which there is a relevant competition between WB-EMS and HIT (Kemmler, Teschler, Weissenfels, et al., 2015). The HIT protocol was designed as single-set training to exertion with different strategies for exhaustion 2-times/week (12 - 14 exercises/session; ≤ 10 - 12 repetitions/exercise; ≈30 min/Session), WB-EMS used an intermitted current protocol (1.5 sessions/week; 6 s impulse – 4 s rest, 85 Hz, 350 µs, rectangular) with (very) slight body movements over 4 months. During the period of the intervention we allowed no changes in nutrition, physical or sports activity. Overall, we were able to record highly relevant and significant improvements in both groups for fat-free mass, appendicular muscle mass, total and abdominal body fat mass, and maximal strength. Slight differences in favor of HIT were found just for fat-free mass, muscle mass of arms and legs as well as maximum strength of leg extension, while the maximum strength of the back straighteners and the abdominal body fat tended to develop better after WB-EMS. This result came as surprise, because we expected a much higher dominance of the very complex and elaborate HIT.
Consequently, for middle-aged men both methods, HIT and WB-EMS appear equally attractive and effective training methods for positively influencing fitness, strength, muscle mass and body fat. As for time efficiency, both methods seem to be suitable for people with limited time resources, whereby the time effort in WB-EMS is clearly more favorable (50 %).
The somewhat lower popularity of HIT in women could be a good opportunity for WB-EMS time-efficient fitness and body composition in this particular group. However, this speculation, supported by a high percentage of female WB-EMS users, should be underpinned by further investigations.
Friedrich-Alexander University of Erlangen-Nuremberg – Institute of Medical Physics
First studies on EMS Training already in 2008 dubject to research so far (selected)
- the effectiveness of EMS Training in the elderly sector
- different EMS frequencies
- the combination of EMS with endurance training
- grossly negligent application of EMS Training and its consequences on health
- comparison between HIT strength training and EMS Training
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